1. Field of the Invention
The invention relates to a container with flexible walls that surround a container interior. At least one electrical sensor projects into the container interior and has at least two electrically conductive plates. The conductivity or impedance of a medium that surrounds the plates can be determined. The plates are connected via connecting lines to a control and regulating unit arranged outside the container interior.
2. Description of the Related Art
US 2011/0187388 A1 discloses a bioreactor with a container with flexible walls that surround a container interior and at least one electrical sensor projecting into the container interior. In this case, electrically conductive plates or electrodes can be used to determine the conductivity or impedance of a medium that surrounds the plates. The plates are connected via connecting lines to a control and regulating unit arranged outside the container interior.
It is disadvantageous in this regard that the sensors or their electrode surfaces are arranged directly on the wall. Although this enables the container, including the sensors, to be folded up, it has the disadvantage that the one or more sensors cannot be adjusted to differing fill levels.
US 2011/0187388 A1 also discloses a container with rigid walls having a sensor arranged within the container interior on the free end of a rigid cylindrical sheathing that is mounted so as to be displaceable within an adapter that penetrates the top wall.
It is disadvantageous in this regard that leaks and contamination may arise between the displaceable sheathing and the adapter. In particular, contamination results if the sheathing is displaced from the exterior into the interior. If the cylindrical sheathing is not connected to the adapter in a displaceable manner, the height of the sensor cannot be adjusted, making it impossible to adjust to differing fill levels. Furthermore, it is also impossible to fold up flat a bioreactor with a container having flexible walls and a sensor arranged in a rigid cylindrical sheathing whose position relative to the fill level remains fixed.
DE 41 42 967 A1 discloses a bioreactor whose container has rigid walls and a top through which a cylindrical measurement probe is introduced from the exterior up to the maximum fill level of the bioreactor in order to eliminate foam. This probe is used to detect foam forming on the surface of the fermentation broth and measure its height. The measurement signal from the probe is fed into a regulating unit arranged outside the container. Depending on the height of the foam above the fermentation broth, a pump installed in an inlet line is actuated and causes an antifoam agent to be fed into the bioreactor from a container.
It is also disadvantageous with regard to this known bioreactor that problems with sealing and contamination between the probe and top or the container interior can occur with a displaceable probe. To the extent the probe is permanently connected to the top, it is no longer possible to adjust the fill level. If different fill levels are to be covered with a fixed probe arrangement using such a probe, the probe is relatively complicated and cost-intensive in structure.
U.S. Pat. No. 5,922,112 A discloses a bioreactor for wastewater that is open on top and has an electrical sensor for foam measurement that projects from above into the container interior. The sensor is connected via a control and regulating unit to a pump arranged in a line between a container containing antifoam agent and the bioreactor.
Furthermore, DE 10 2010 007 559 A1 discloses a bioreactor with a container with flexible walls that has an optical sensor for foam measurement that can be laterally arranged from the exterior. This optical sensor, which has essentially proven its usefulness, is reusable as it does not come into contact with the container interior, the fluid contained therein or any potential foam layer, and because it is separated from the container interior by a transparent window arranged in the container wall. Such an optical sensor is relatively cost-intensive, particularly if it is able to detect differing fill levels.
The present invention seeks to solve the problem of providing a bioreactor having a container with flexible walls and at least one low-cost electrical sensor for measuring the conductivity or impedance of a medium arranged in the container. The container with the sensor should be suitable for single use and be capable of being folded up to a small volume when empty.